diff --git a/routers/web/repo/branch.go b/routers/web/repo/branch.go
index 05f06a3ceb..53bd599b0d 100644
--- a/routers/web/repo/branch.go
+++ b/routers/web/repo/branch.go
@@ -231,7 +231,7 @@ func CreateBranch(ctx *context.Context) {
 			if len(e.Message) == 0 {
 				ctx.Flash.Error(ctx.Tr("repo.editor.push_rejected_no_message"))
 			} else {
-				flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+				flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 					"Message": ctx.Tr("repo.editor.push_rejected"),
 					"Summary": ctx.Tr("repo.editor.push_rejected_summary"),
 					"Details": utils.SanitizeFlashErrorString(e.Message),
diff --git a/routers/web/repo/editor.go b/routers/web/repo/editor.go
index 80c212b698..4f26c0c521 100644
--- a/routers/web/repo/editor.go
+++ b/routers/web/repo/editor.go
@@ -382,7 +382,7 @@ func editFilePost(ctx *context.Context, form forms.EditRepoFileForm, isNewFile b
 			if len(errPushRej.Message) == 0 {
 				ctx.RenderWithErr(ctx.Tr("repo.editor.push_rejected_no_message"), tplEditFile, &form)
 			} else {
-				flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+				flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 					"Message": ctx.Tr("repo.editor.push_rejected"),
 					"Summary": ctx.Tr("repo.editor.push_rejected_summary"),
 					"Details": utils.SanitizeFlashErrorString(errPushRej.Message),
@@ -394,7 +394,7 @@ func editFilePost(ctx *context.Context, form forms.EditRepoFileForm, isNewFile b
 				ctx.RenderWithErr(flashError, tplEditFile, &form)
 			}
 		} else {
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.editor.fail_to_update_file", form.TreePath),
 				"Summary": ctx.Tr("repo.editor.fail_to_update_file_summary"),
 				"Details": utils.SanitizeFlashErrorString(err.Error()),
@@ -590,7 +590,7 @@ func DeleteFilePost(ctx *context.Context) {
 			if len(errPushRej.Message) == 0 {
 				ctx.RenderWithErr(ctx.Tr("repo.editor.push_rejected_no_message"), tplDeleteFile, &form)
 			} else {
-				flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+				flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 					"Message": ctx.Tr("repo.editor.push_rejected"),
 					"Summary": ctx.Tr("repo.editor.push_rejected_summary"),
 					"Details": utils.SanitizeFlashErrorString(errPushRej.Message),
@@ -797,7 +797,7 @@ func UploadFilePost(ctx *context.Context) {
 			if len(errPushRej.Message) == 0 {
 				ctx.RenderWithErr(ctx.Tr("repo.editor.push_rejected_no_message"), tplUploadFile, &form)
 			} else {
-				flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+				flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 					"Message": ctx.Tr("repo.editor.push_rejected"),
 					"Summary": ctx.Tr("repo.editor.push_rejected_summary"),
 					"Details": utils.SanitizeFlashErrorString(errPushRej.Message),
diff --git a/routers/web/repo/issue.go b/routers/web/repo/issue.go
index e74049810a..879cb871e7 100644
--- a/routers/web/repo/issue.go
+++ b/routers/web/repo/issue.go
@@ -9,6 +9,7 @@ import (
 	stdCtx "context"
 	"errors"
 	"fmt"
+	"html/template"
 	"math/big"
 	"net/http"
 	"net/url"
@@ -1022,7 +1023,7 @@ func NewIssue(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplIssueNew)
 }
 
-func renderErrorOfTemplates(ctx *context.Context, errs map[string]error) string {
+func renderErrorOfTemplates(ctx *context.Context, errs map[string]error) template.HTML {
 	var files []string
 	for k := range errs {
 		files = append(files, k)
@@ -1034,14 +1035,14 @@ func renderErrorOfTemplates(ctx *context.Context, errs map[string]error) string
 		lines = append(lines, fmt.Sprintf("%s: %v", file, errs[file]))
 	}
 
-	flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+	flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 		"Message": ctx.Tr("repo.issues.choose.ignore_invalid_templates"),
 		"Summary": ctx.Tr("repo.issues.choose.invalid_templates", len(errs)),
 		"Details": utils.SanitizeFlashErrorString(strings.Join(lines, "\n")),
 	})
 	if err != nil {
 		log.Debug("render flash error: %v", err)
-		flashError = ctx.Locale.TrString("repo.issues.choose.ignore_invalid_templates")
+		flashError = ctx.Locale.Tr("repo.issues.choose.ignore_invalid_templates")
 	}
 	return flashError
 }
@@ -3324,7 +3325,7 @@ func ChangeIssueReaction(ctx *context.Context) {
 		return
 	}
 
-	html, err := ctx.RenderToString(tplReactions, map[string]any{
+	html, err := ctx.RenderToHTML(tplReactions, map[string]any{
 		"ctxData":   ctx.Data,
 		"ActionURL": fmt.Sprintf("%s/issues/%d/reactions", ctx.Repo.RepoLink, issue.Index),
 		"Reactions": issue.Reactions.GroupByType(),
@@ -3431,7 +3432,7 @@ func ChangeCommentReaction(ctx *context.Context) {
 		return
 	}
 
-	html, err := ctx.RenderToString(tplReactions, map[string]any{
+	html, err := ctx.RenderToHTML(tplReactions, map[string]any{
 		"ctxData":   ctx.Data,
 		"ActionURL": fmt.Sprintf("%s/comments/%d/reactions", ctx.Repo.RepoLink, comment.ID),
 		"Reactions": comment.Reactions.GroupByType(),
@@ -3574,8 +3575,8 @@ func updateAttachments(ctx *context.Context, item any, files []string) error {
 	return err
 }
 
-func attachmentsHTML(ctx *context.Context, attachments []*repo_model.Attachment, content string) string {
-	attachHTML, err := ctx.RenderToString(tplAttachment, map[string]any{
+func attachmentsHTML(ctx *context.Context, attachments []*repo_model.Attachment, content string) template.HTML {
+	attachHTML, err := ctx.RenderToHTML(tplAttachment, map[string]any{
 		"ctxData":     ctx.Data,
 		"Attachments": attachments,
 		"Content":     content,
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index fdddcba2c8..c93d342e62 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1159,7 +1159,7 @@ func UpdatePullRequest(ctx *context.Context) {
 	if err = pull_service.Update(ctx, issue.PullRequest, ctx.Doer, message, rebase); err != nil {
 		if models.IsErrMergeConflicts(err) {
 			conflictError := err.(models.ErrMergeConflicts)
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.pulls.merge_conflict"),
 				"Summary": ctx.Tr("repo.pulls.merge_conflict_summary"),
 				"Details": utils.SanitizeFlashErrorString(conflictError.StdErr) + "<br>" + utils.SanitizeFlashErrorString(conflictError.StdOut),
@@ -1173,7 +1173,7 @@ func UpdatePullRequest(ctx *context.Context) {
 			return
 		} else if models.IsErrRebaseConflicts(err) {
 			conflictError := err.(models.ErrRebaseConflicts)
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.pulls.rebase_conflict", utils.SanitizeFlashErrorString(conflictError.CommitSHA)),
 				"Summary": ctx.Tr("repo.pulls.rebase_conflict_summary"),
 				"Details": utils.SanitizeFlashErrorString(conflictError.StdErr) + "<br>" + utils.SanitizeFlashErrorString(conflictError.StdOut),
@@ -1305,7 +1305,7 @@ func MergePullRequest(ctx *context.Context) {
 			ctx.JSONError(ctx.Tr("repo.pulls.invalid_merge_option"))
 		} else if models.IsErrMergeConflicts(err) {
 			conflictError := err.(models.ErrMergeConflicts)
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.editor.merge_conflict"),
 				"Summary": ctx.Tr("repo.editor.merge_conflict_summary"),
 				"Details": utils.SanitizeFlashErrorString(conflictError.StdErr) + "<br>" + utils.SanitizeFlashErrorString(conflictError.StdOut),
@@ -1318,7 +1318,7 @@ func MergePullRequest(ctx *context.Context) {
 			ctx.JSONRedirect(issue.Link())
 		} else if models.IsErrRebaseConflicts(err) {
 			conflictError := err.(models.ErrRebaseConflicts)
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.pulls.rebase_conflict", utils.SanitizeFlashErrorString(conflictError.CommitSHA)),
 				"Summary": ctx.Tr("repo.pulls.rebase_conflict_summary"),
 				"Details": utils.SanitizeFlashErrorString(conflictError.StdErr) + "<br>" + utils.SanitizeFlashErrorString(conflictError.StdOut),
@@ -1348,7 +1348,7 @@ func MergePullRequest(ctx *context.Context) {
 			if len(message) == 0 {
 				ctx.Flash.Error(ctx.Tr("repo.pulls.push_rejected_no_message"))
 			} else {
-				flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+				flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 					"Message": ctx.Tr("repo.pulls.push_rejected"),
 					"Summary": ctx.Tr("repo.pulls.push_rejected_summary"),
 					"Details": utils.SanitizeFlashErrorString(pushrejErr.Message),
@@ -1525,7 +1525,7 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 				ctx.JSONError(ctx.Tr("repo.pulls.push_rejected_no_message"))
 				return
 			}
-			flashError, err := ctx.RenderToString(tplAlertDetails, map[string]any{
+			flashError, err := ctx.RenderToHTML(tplAlertDetails, map[string]any{
 				"Message": ctx.Tr("repo.pulls.push_rejected"),
 				"Summary": ctx.Tr("repo.pulls.push_rejected_summary"),
 				"Details": utils.SanitizeFlashErrorString(pushrejErr.Message),
@@ -1534,8 +1534,7 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 				ctx.ServerError("CompareAndPullRequest.HTMLString", err)
 				return
 			}
-			ctx.Flash.Error(flashError)
-			ctx.JSONRedirect(ctx.Link + "?" + ctx.Req.URL.RawQuery) // FIXME: it's unfriendly, and will make the content lost
+			ctx.JSONError(flashError)
 			return
 		}
 		ctx.ServerError("NewPullRequest", err)
diff --git a/services/context/context_response.go b/services/context/context_response.go
index 829bca1f59..372b4cb38b 100644
--- a/services/context/context_response.go
+++ b/services/context/context_response.go
@@ -6,6 +6,7 @@ package context
 import (
 	"errors"
 	"fmt"
+	"html/template"
 	"net"
 	"net/http"
 	"net/url"
@@ -104,11 +105,11 @@ func (ctx *Context) JSONTemplate(tmpl base.TplName) {
 	}
 }
 
-// RenderToString renders the template content to a string
-func (ctx *Context) RenderToString(name base.TplName, data map[string]any) (string, error) {
+// RenderToHTML renders the template content to a HTML string
+func (ctx *Context) RenderToHTML(name base.TplName, data map[string]any) (template.HTML, error) {
 	var buf strings.Builder
-	err := ctx.Render.HTML(&buf, http.StatusOK, string(name), data, ctx.TemplateContext)
-	return buf.String(), err
+	err := ctx.Render.HTML(&buf, 0, string(name), data, ctx.TemplateContext)
+	return template.HTML(buf.String()), err
 }
 
 // RenderWithErr used for page has form validation but need to prompt error to users.
diff --git a/web_src/js/features/common-global.js b/web_src/js/features/common-global.js
index f90591aff3..c53d43cbb2 100644
--- a/web_src/js/features/common-global.js
+++ b/web_src/js/features/common-global.js
@@ -91,19 +91,24 @@ async function fetchActionDoRequest(actionElem, url, opt) {
       } else {
         window.location.reload();
       }
+      return;
     } else if (resp.status >= 400 && resp.status < 500) {
       const data = await resp.json();
       // the code was quite messy, sometimes the backend uses "err", sometimes it uses "error", and even "user_error"
       // but at the moment, as a new approach, we only use "errorMessage" here, backend can use JSONError() to respond.
-      showErrorToast(data.errorMessage || `server error: ${resp.status}`);
+      if (data.errorMessage) {
+        showErrorToast(data.errorMessage, {useHtmlBody: data.renderFormat === 'html'});
+      } else {
+        showErrorToast(`server error: ${resp.status}`);
+      }
     } else {
       showErrorToast(`server error: ${resp.status}`);
     }
   } catch (e) {
     console.error('error when doRequest', e);
-    actionElem.classList.remove('is-loading', 'small-loading-icon');
-    showErrorToast(i18n.network_error);
+    showErrorToast(`${i18n.network_error} ${e}`);
   }
+  actionElem.classList.remove('is-loading', 'small-loading-icon');
 }
 
 async function formFetchAction(e) {
diff --git a/web_src/js/modules/toast.js b/web_src/js/modules/toast.js
index fa075aed48..d64359799c 100644
--- a/web_src/js/modules/toast.js
+++ b/web_src/js/modules/toast.js
@@ -21,13 +21,12 @@ const levels = {
 };
 
 // See https://github.com/apvarun/toastify-js#api for options
-function showToast(message, level, {gravity, position, duration, ...other} = {}) {
+function showToast(message, level, {gravity, position, duration, useHtmlBody, ...other} = {}) {
   const {icon, background, duration: levelDuration} = levels[level ?? 'info'];
-
   const toast = Toastify({
     text: `
       <div class='toast-icon'>${svg(icon)}</div>
-      <div class='toast-body'>${htmlEscape(message)}</div>
+      <div class='toast-body'>${useHtmlBody ? message : htmlEscape(message)}</div>
       <button class='toast-close'>${svg('octicon-x')}</button>
     `,
     escapeMarkup: false,